Process of making color printing plates



Se t. 13, 1938. E. D. LAKE 2,129,945 v PROCESS OF-M I LOR P TING PLATES NAME 2b mgrgn f ATTORNEY Patented Sept. 13, 1938 PROCESS OF MAKING COLOR PRINTING PLATES Eismore E. Lake, Oakland, Calif.

Application October 15, 1935, Serial No. 45,074

2 Claims.

This invention relates to the production of plates used in multi-color lithography and print? ing processes.

It is an object of the invention to materially lessen the amount of work required to produce color printing plates for the uses 'referred to.

Another object of the invention is to provide a process for making color printing plates which insures that the edges of color areas of each plate will register exactly when printedthereby preventing overlapping of colors on' the finished print.

Another object of the invention is to provide a process of making color-printing-plates which,

because of eliminatingall of the hand work heretofore required to produce such plates, enables the plates to be produced very economically. Referring to the drawing: Figure 1 is a plan view exemplifying a threecolor print which the plates, made according to 1 my process, are capable of producing.

Figure 2 is a,plan view of the master drawing from which the separate negatives are photographically produced.

Figures 3, 4 and are plan views of positive representations of the several negatives obtained by photographing the master drawing.

The process described herein is not to be confused with those used for reproducing paintings or the like, wherein, overlapping or superposing of different color areas is employed to produce different color tones on the resulting print. My process is only applicable to prints in which each color completely covers and occupies a separate, sharply defined area.

The method commonly employed in the production of printing plates for multi-color printing is to make a black and white master drawing of the print required, make a photographic negative of this drawing, make exposures from this negative on the sensitized'surface of each metal printing plate, develop these exposures, and then rout out or etch away all areas of each plate except those which correspond to areas of like color on the finished print. After completion of these plates, proof prints must be 'pulled to ascertain whether there are any overlaps, or gaps, between different color areas, whereupon the faulty plates must be trimmed or built up to correct these imperfections.

As will be evident, considerable hand work of skilled and highly paid labor is required to produce satisfactory printing plates and as a result the production of the latter is quite expensive.

By my improved process I contemplate producing the areas of each plate, which will print a given color on the finished print, entirely photomechanically thereby entirely eliminating all hand engraving of the plates and insuring that the component areas of the print will register exactly, thereby dispensing with the necessity of pulling proof prints from the plates.

Describing my process in detail, let us assume that the label 6, shown in Figure 1,-is to be reproduced.- The printed matter thereon consists of a background I, which may be a green shield, upon which appears black letters 8, each having a white border 9'. The colors shown were chosen for illustration only, as any combination of colors may be used.

The first step in my process is to make a master drawing I0, shown in Figure 2, but instead of reproducing the printed matter in its original colors, primary colors only are used. For instance,. the area ll representing the shield, is colored red, the areas l2 representing the letters 8 are colored yellow, and the areas l3 bordering each letter are colored blue.

The master drawing is now mounted before a camera in which a red filteris mounted and the plate, or film, is exposed thereby resulting in a negative i4, shown in Figure 3, which defines only the area colored red in the master drawing.

A new plate is loaded into the camera, the red filter is replaced by a blue filter, and another exposure is made, this time resulting in'the negative l5 shown in Figure 4, which defines only the blue areas bordering the letters on the master drawing. I

Another plate is now inserted in the camera, the blue filter is replaced by a yellow filter and, after exposure, the resulting negative l6, Figure 5, will be found to define only the yellow letters of the master drawing. I 4

Each of these three negatives may now be placed on the pre-sensitized surfaces of separate printing plates, exposures made thereof,.and the printing plates developed and etched, whereupon the plates are ready for printing, no further work of any kind being required thereon.

Since each negative I4, I5 and I6 was produced with the same setting of the camera. and the master drawing, all of the negatives are photo-mechanically perfect and will, if superposed, register exactly, therefore it is obvious that the printing plates made therefrom,- since these latter are contact prints made from the negatives, will also be in perfect registry.

In summing up therefore it will be seen that the main step in my process is to produce a master drawing of the print required in which the areas desired to be separated are each given a color which can be separated from the others by use of the camera's color filter, thus resulting in the production of negatives which contain only those areas of the master drawing which correspond, in color, to the color filter used, all other areas being masked out.

It will be evident that since no hand work in routing out our building up the printing. plates, as in the processes generally used, is necessary, printing plates are capable of production, by my process, for a fraction of the cost compared to that of printing plates made by the old method. In addition to this, the plates may be mounted directly on the press without the necessity of pulling proof prints therefrom, since the printer is aware that because of the photo-mechanical perfection of the plates, correct registry of the color areas of the finished print is assured.

I claim:

1. The method of multicolor printing to reproduce an original object composed of a plurality 1 of distinct, non-overlapping colored areas, each of said areas being uniformly colored and at least two of said areas being of different hues relative to one another, which consists in preparing a single master drawing of said original by substituting for the separate hues in the colored areas of the original several distinct hues in'the corresponding component areas-of the drawing and successively photographing the master drawing through each of a plurality of differently colored filters corresponding in number to the number of hues of the original, said several hues of the drawing corresponding in color to the filters used irrespective of the colors of the original so that substantially complete separation of the colors occurs, placing each separation negative in engagement with the presensitized surface of a printing plate blank and photographically reproducing each negative upon a printing plate, etching each plate, and printing in superimposition each plate with an ink corresponding in color to the colored area of the original which such plate represents.

2. The method of multicolor printing to reproduce an original object composed of a plurality of distinct non-overlapping colored and uncolored areas, each of said colored areas being uniformly colored and at least two of said areas being of different hues relative to one another, which consists in preparing a single master draw-- ing of said original by substituting in the master drawing for the said distinct separate colored and uncolored areas of the original several distinct hues in the corresponding component areas of the drawing and successively photographing the master drawing through each of a plurality of colored filters corresponding in number to the number of areas of the original, said several hues of the drawing corresponding in color to the filters used irrespective of the colors or lack of color in the areas of the original so that substantially complete separation of the colors occurs, placing each separation negative in engagement with the presensitized surface of a printing plate blank and photographically reproducing each negative upon a printing plate, etching each plate, and printing in superimposition each color plate with an ink corresponding in color to the colored area of .the original which such plate represents.

ELSMORE D. LAKE. 

